Method for constructing a chair-type, self-supported earth retaining wall

ABSTRACT

The present invention provides a method for constructing a chair-type, self-supported earth retaining wall used for retaining external forces such as earth pressure prior to an excavation. The method of the present invention forms a first column of piles having a plurality of piles arranged along the circumference of the region to be excavated. Subsequently, the method comprises forming a second column of piles having a plurality of piles by consecutively perforating a plurality of holes by a predetermined spacing at predetermined positions outwardly from the first column of piles, along the circumference of the region to be excavated, inserting H-beams into the respective holes, filling left and right spaces of the webs of the H-beams with soil, and filling the outer spaces of the flanges of the H-beams with a flowable stiffening material. The method subsequently comprises interconnecting the first column of piles and the second column of piles by a connection member. The first column of piles and the second column of piles are formed along the circumference of the region to be excavated, with an outward spacing, and connected to each other by the connection member. 
     The present invention provides a method for constructing a chair-type, self-supported earth retaining wall used for supporting external forces such as earth pressure prior to an excavation. The method of the present invention comprises forming a first pile array  20  having a plurality of piles  22  arranged along a circumference of an region to be excavated. Subsequently, the method comprises forming a second pile array  30  having a plurality of piles arranged along a circumference of the to-be-excavated region by consecutively drilling a plurality of boreholes  31  at predetermined intervals at predetermined positions outwardly spaced apart from the first pile array, inserting H-beams into the respective boreholes, filling left and right spaces of webs  34  of the H-beams  32  with soil  40 , and filling the outer spaces of flanges  36  of the H-beams with a flowable hardening material  50.    
     The method subsequently comprises fixedly interconnecting the first pile array and the second pile array using a connection member. The first pile array and the second pile array are formed in such a fashion as to be outwardly spaced apart from each other along the circumferences of the to-be-excavated region, and are connected to each other by the connection member to construct an underground earth retaining wall.

TECHNICAL FIELD

The present invention relate to a method for constructing a chair-type,self-supported earth retaining wall, and particularly to, such a methodfor constructing a chair-type, self-supported earth retaining wall, inwhich an earth retaining wall used for supporting an external force suchas earth pressure or the like prior to an excavation can be constructedby a supporting construction technique employing an improved double-rowpile structure so as to complement various shortcomings involved in aconventional temporary facility construction technique such as a strutsupporting construction technique, an earth anchor constructiontechnique or the like.

BACKGROUND ART

In general, when filling the ground, cutting the ground, or drilling theground, and the like are performed, while a slope surface is generallyformed to maintain the stability of the ground. However, when theexcavation is performed to improve the utility of the land moreeffectively or to improve the foundation of a structure in an urban areaand construct a basement of a building, a vertical excavation isperformed without the formation of the slope surface. In this regard, anearth retaining wall is necessarily installed around the vertical wallsurface to prevent the breakage of the adjoining ground due to thevertical excavation. However, a temporary facility constructiontechnique for installing the earth retaining wall should be selected inconsideration of the conditions of the earth, the conditions of theground, the effect of the earth retaining wall on the surroundings ofthe ground, construction expense, construction period, and theconstruction capacity, and the like, as well as the characteristics ofthe respective construction methods sufficiently.

Nowadays, one of the most generally known techniques of constructing theearth retaining wall is a strut supporting construction technique. Sincethis construction technique is designed to endure the soil pressure bythe compression force of the strut, a plurality of struts is denselyarranged at intervals of several meters in the longitudinal andtransverse directions. Accordingly, in case of a large drilling work,the use of a large quantity of steel sheets greatly increases theconstruction expense, and the arranged struts obstruct the field workssuch as the movement of the drilling equipment, the conveyance of thedrilled earth and sand, and the construction materials, and the like. Inaddition, the above strut supporting construction technique causesimpediments to works of the reinforcing steel bar of a structure or amold, thereby reducing the working efficiency. Also, in the strutsupporting construction technique, a number of through-holes produced inthe structure causes problems of durability and waterproof property ofan completed underground structure.

Meanwhile, there has been proposed an earth anchor constructiontechnique as a method of constructing the earth retaining wall withoutany strut among the conventional earth retaining constructiontechniques. This construction technique has an advantage in that sincesufficient inside space can be secured, following works become easy.However, this construction technique has serious disadvantages in thatthere is a restriction in the conditions for the construction field incase of downtown area construction work because it could encroachadjoining private lands, and the construction expense becomes high incase of non-large sized drilling works.

As another conventional art, there is a soil nailing constructiontechnique in which boreholes are formed at the rear side of the drillingwall together with the drilling work, nails are inserted into theboreholes and then grouts are filled therein, and shotcrete is cast ontothe wall surface, thereby forming the earth retaining wall body. Sincethis construction technique is simple in construction and has noimpediment due to struts, it has advantages in that construction periodof a following process can be reduced, and the soil pressure acting onthe underground structure is reduced, thereby decreasing thecross-section of the structure. However, in case of a ground having ahigh underground water level and a ground having a subsidence property,there is a risk of slope breakage, and the modification of the inclinedsurface due to cutting off of the earth is serious, thereby causing thesinking of the adjoining ground. Further, the above soil nailingconstruction technique has a disadvantage in that it is difficult toapply to the ground of specific conditions, and it requires a carefulattention.

As still another conventional art, there has been proposed a rakerconstruction technique in which an earth retaining wall is firstconstructed, a slope surface is formed at the inside of the earthretaining wall, a reaction force is applied to the previouslyconstructed foundation structure, an inclined strut is installed on theearth retaining wall to thereby progress the drilling work. Thisconstruction technique has an advantage in that it is simple inconstruction, requires less strut holes, and the inclined strut is shortin length, thereby decreasing contraction or flow of a moving jointportion. However, there occur problems in that stability of the inclinedsurface is difficult to secure in a weak ground, it is improper for adeep drilling work, a space is narrow and the workability is poor at thetime of constructing a structure in the raker.

As yet another conventional art, there has bee proposed a prestressedgirth construction technique. This construction technique is one ofwidening an interval between the struts by additionally installing agirth above the previously installed girth to tension a steel wire,thereby reinforcing an additional girth or a flange of an existingH-beam. However, the above construction technique has disadvantages inthat since the steel wire is disposed linearly, and a moment produced inthe girth due to the soil pressure is different from a resistance momentproduced by prestressing, so that an unbalanced moment always acts on inthe members, and the girth is weak to a local unbalanced load when thelength thereof is made long. In addition, such a construction techniquehas a limitation in extending the length of the prestressed girthbecause of restriction in increasing eccentricity due to limitation inthe rigidity of the installation device.

As a further conventional art, there has been proposed a truss girthconstruction technique, which is expected to be applicable to a case ofa relatively shallow depth, and in which H-beams are installed doubly ina lattice shape at the adjoining place of the ground surface, so thatthe soil pressure can be received by the trusses of two layers installedat the upper portion by reinforcing the beams with the vertical membersand inclined members. This construction technique was devised toovercome difficulties arising in the drilling and construction of themain structure due to the struts of the temporary facility structure forsupporting the ground, and is one which can be used when a largerstructure is disposed at the lower portion of the drilled ground and asmaller structure is disposed at the upper portion of the drilledground.

The above temporary facility construction techniques for constructingthe earth retaining wall mostly employ H-beam to construct the earthretaining wall. In some cases, sheet piles are often used, but in thecase where there is no great need for a waterstop and the like, an earthretaining wall installation work is performed in such a fashion thatH-beams are inserted into boreholes at intervals of approximately twometers, and then laggings, i.e., soil retaining plates made of wood arefitted between the H-beams while digging a region to be excavated. Insuch a temporary facility construction technique for constructing theearth retaining wall, a method of inserting the H-beams into the groundmay include driving the H-beams into soil using a direct pile drivingtechnique. However, there frequently occurs the case where a piledriving work is not performed smoothly because of gravel existing insoil or other ground conditions. In particular, the H-beams are insertedinto the ground by a ground boring method employing Augering instead ofthe pile driving in most fields due to a driving noise generated duringthe pile driving. In the case where the construction is performed in theabove manner, when the H-beams are inserted into the boreholes of theground, a noise is prevented from being generated during the piledriving and the construction can be advantageously continued without anyinterruption of the excavation by the gravel and the like existing inthe ground.

In this case, as shown in FIG. 10, since a clearance is required forinsertion of the H-beam 520 between a borehole 500 formed by theaugering technique and an H-beam 520 inserted into the borehole 500, theinserted H-beam 520 is held under the condition where a displacement canoccur within a range of about of 10 cm. Thus, the borehole 500 is filledup with several kinds of soil 530 including on-site soil after insertionof the H-beam 520 in order to minimize a possibility of the displacementof about 10 cm on the construction site. However, this filling workcannot be performed well due to a relatively deep boring depth ascompared to a small clearance space because the boring depth of theborehole 500 is more than 10 m. In addition, although the filling workis performed well, soil must be well tamped down in order to achieve anexpected and desired effect. However, in this tamping work, it isdifficult to expect the desired effect at the regions beyond a regionwithin a range of 1 m on the ground surface. For this reason, as shownin FIG. 11, there occurs a problem in that an initial H-beam 520 isinclined to be at a position 520′ toward a to-be-excavated region in theborehole 500 at the time of digging the to-be-excavated region.

The problem of the excessive displacement of the H-beam can be solved byapplying a method of inserting the H-beam 520 into the borehole 500 andthen injecting cement paste 540 into the borehole 500 in a conventionalconstruction method. However, such a method of employing the cementpaste 540 entails problems in that it makes difficult a pullout work forcollecting the inserted H-beam 520 after the completion of theconstruction, and hardened cement lumps surrounding the surface of theH-beam 520 must be removed for the reuse of the H-beam although theinserted H-beam 520 is collected. Accordingly, such a cement pasteinjection method involves a drawback in that it is difficult to apply tothe construction in which the H-beam must be substantially recollected.

In particular, in the case where the H-beam is constructed in aself-supported earth retaining construction method, the fillingwork-associated problem is very important. That is, the present inventorhas proposed a self-supported earth retaining construction method in PCTinternational publication No. WO 2007/117050 entitled “UNDERGROUNDRETAINING WALL FOR PUBLIC WORKS AND METHOD FOR CONSTRUCTING THE SAME”.In the self-supported earth retaining construction method, a load actionis depicted as shown in FIG. 12. It can be seen from FIG. 12 that thereis a great effect of displacement of the H-beam occurring due to ahorizontal force (active earth pressure and passive earth pressure)acting on the H-beam. Thus, it is required that the filling work of theborehole should be performed entirely. However, as mentioned above, theearth retaining construction method encounters many drawbacks in termsof construction. In most self-supported earth retaining construction inwhich the H-beams must be collected, an incomplete borehole filling workcauses great displacement of the self-supported earth retaining wall,which contributes to a reduction in self-supporting capability.

DISCLOSURE OF INVENTION Technical Problem

Accordingly, the present invention has been made in order to satisfy theabove-mentioned necessities, and it is an object of the presentinvention to provide a method for constructing a novel chair-type,self-supported earth retaining wall, which can utilize a limited landefficiently and eliminate the necessity of using struts in ato-be-excavated region where an architectural construction is executedto improve economic efficiency and construction capacity of a subsequentwork, and which can resolve a problem of an encroachment into adjacentprivate lands and can further reduce land settlement and displacementcaused by the temporary facility construction work, thereby minimizing adamage due to earth excavation and maximizing the excavatable depth.

Another object of the present invention is to prove a method forconstructing a novel chair-type, self-supported earth retaining wall,which can facilitate the reuse of H-beams and can effectively preventthe displacement of the H-beams occurring in boreholes in constructionof an earth retaining wall used for supporting an external force such asearth pressure or the like.

Particularly, yet another object of the present invention is to providean advanced method for constructing a chair-type, self-supported earthretaining wall, which can resolve a problem of an incomplete boreholefilling work inducing the displacement of the H-beams and can facilitatethe collection of the H-beams after the construction to maintaineconomic efficiency and construction capacity and resolve a displacementoccurrence problem, thereby remarkably improving the performance of anearth retaining construction method employing a double-row pilestructure in the self-supported earth retaining construction methodproposed by the present inventor in PCT international publication No. WO2007/117050 entitled “UNDERGROUND RETAINING WALL FOR PUBLIC WORKS ANDMETHOD FOR CONSTRUCTING THE SAME”.

Technical Solution

To achieve the above objects, in one aspect, the present inventionprovides a method for constructing a chair-type, self-supported earthretaining wall used for supporting external forces such as earthpressure, the method includes the steps of: forming a first pile arrayhaving a plurality of piles arranged along a circumference of an regionto be excavated; forming a second pile array having a plurality of pilesarranged along a circumference of the to-be-excavated region byconsecutively drilling a plurality of boreholes at predeterminedintervals at predetermined positions outwardly spaced apart from thefirst pile array along the circumference of the to-be-excavated region,inserting H-beams into the respective boreholes, filling left and rightspaces of webs of the H-beams with soil, and filling the outer spaces offlanges of the H-beams with a flowable hardening material; and fixedlyinterconnecting the first pile array and the second pile array using aconnection member, whereby the first pile array and the second pilearray are formed in such a fashion as to be outwardly spaced apart fromeach other along the circumferences of the to-be-excavated region, andare connected to each other by the connection member to construct anunderground earth retaining wall.

In the method for constructing a chair type, self-supported earthretaining wall according to the present invention, the plurality ofpiles of the first pile array may be formed by consecutively drilling aplurality of boreholes at predetermined intervals along thecircumference of the to-be-excavated region, inserting H-beams into therespective boreholes, filling left and right spaces of webs of theH-beams with soil, and filling the outer spaces of flanges of theH-beams with a flowable hardening material.

In the method for constructing a chair-type, self-supported earthretaining wall according to the present invention, the plurality ofpiles of the first pile array may be formed of any one selected from thegroup consisting of H-piles and soil retaining plates, sheet piles,cast-in-place piles, and soil cement walls.

In the method for constructing a chair-type, self-supported earthretaining wall according to the present invention, the step of fixedlyinterconnecting the first pile array and the second pile array using aconnection member may include the following steps of: joining a firstgirth to the plurality of piles constituting the first pile array suchthat the piles are arranged in parallel with each other; joining asecond girth to the plurality of piles constituting the second pilearray such that the piles are arranged in parallel with each other; andmounting fixing bars on the first girth and the second girth in such afashion as to be joined at both ends thereof to the first girth and thesecond girth.

In the method for constructing a chair-type, self-supported earthretaining wall according to the present invention, the step of fixedlyinterconnecting the first pile array and the second pile array using aconnection member may include the following steps of: forming asub-excavation region communicating extending from the second pile arrayon the ground to the to-be-excavated region during excavation of theto-be-excavated region; joining loggings to the second pile array whileforming the sub-excavation region along the second pile array; joining afirst girth to the plurality of piles constituting the first pile arraysuch that the piles are arranged in parallel with each other on theground of the sub-excavation region; joining a second girth to theplurality of piles constituting the second pile array such that thepiles are arranged in parallel with each other; mounting fixing bars onthe first girth and the second girth in such a fashion as to be joinedat both ends thereof to the first girth and the second girth; andjoining loggings to the first pile array while forming theto-be-excavated region along the first pile array.

Advantageous Effects

The method for constructing a chair-type, self-supported earth retainingwall of the present invention can improve several disadvantages involvedin an existing temporary facility construction technique such as thestrut supporting construction technique, the earth anchor constructiontechnique, or the like. That is, according to the present invention, thenecessity of using struts is eliminated, so that the quantity of thesteel sheets used is reduced, thereby saving the construction expense,shortening the construction period, making the construction of heavyequipment in the excavation site smooth, and facilitating a subsequentmold work to improve the construction capacity. In addition, since thepresent invention implements a self-supported temporary facilitystructure to resolve a problem of an encroachment into adjacent privatelands occurring when the anchor is installed on the ground, therestriction in the downtown area construction work, etc., is mostlyremoved as compared to the earth anchor construction technique.Moreover, the present invention can further reduce land settlement anddisplacement caused by the temporary facility construction work therebyminimizing a damage of adjacent structure due to earth excavation andfurther increasing the excavatable depth as compared to theself-supported earth retaining construction method that has beenproposed by the present inventor in PCT international publication No. WO2007/117050 entitled “UNDERGROUND RETAINING WALL FOR PUBLIC WORKS ANDMETHOD FOR CONSTRUCTING THE SAME”. In particular, the flowable hardeningmaterial such as cement paste is charged into the outer spaces of bothflanges of the H-beam, soil such on-site soil is poured into the innerspaces of the both flanges of the H-beam to support the H-beam in theboreholes. Thus, the H-beam is discarded into the ground in case of anexisting traditional construction method, but the reuse of the H-beam isfacilitated and the displacement the H-beam occurring in the boreholescan be effectively prevented in case of a novel construction method.Accordingly, since the stable support of the H-beams within theboreholes minimizes the occurrence of the displacement of the earthretaining wall, the merit of the self-supported earth retaining wallemploying a double-row pile structure can be maximized. In addition,since the present invention uses various walls such as cast-in-placepiles (CIPs), soil cement walls (SCWs), sheet piles, and the like as thefirst pile array, it enables the inventive earth retaining wall to bindto various kinds of walls to provide a water stopping function andexhibit a heaving prevention effect, thereby ensuring its excellentusability. Moreover, the chair-type, self-supported earth retaining wallconstruction method according to the present invention can be utilizedcomplementarily together with the existing traditional earth retainingconstruction method. In case of this construction, the conventionalconstruction method can show the effect of the present invention andsimultaneously can further increase the underground excavation depth. Ifthe present invention is used together with the strut supportingconstruction method as a complementary supporting construction method,the construction distance and use quantity of the struts is reduced,thereby improving the construction capacity and the economic efficiency.In addition, if the present invention is used together with the earthanchor construction method as a complementary supporting constructionmethod, the construction distance and use quantity of the earth anchorsis reduced, thereby improving the construction capacity and the economicefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top plan view illustrating an earth retaining wallconstructed by a method for constructing a chair-type, self-supportedearth retaining wall according to the present invention;

FIG. 2 is a view for explaining a method for constructing a chair-type,self-supported earth retaining wall according to a preferred embodimentof the present invention;

FIG. 3 is a perspective view illustrating a constitution of an earthretaining wall constructed by the method for constructing thechair-type, self-supported earth retaining wall shown in FIG. 2;

FIG. 4 is a view for explaining a method for constructing a chair-type,self-supported earth retaining wall according to another preferredembodiment of the present invention;

FIG. 5 is a perspective view illustrating a constitution of an earthretaining wall constructed by the method for constructing thechair-type, self-supported earth retaining wall shown in FIG. 4;

FIG. 6 is a view for explaining a second pile array construction methodin a method for constructing a chair-type, self-supported earthretaining wall according to the preferred embodiment of the presentinvention;

FIG. 7 is a view for explaining the applicable examples of a connectionmember in a method for constructing a chair-type, self-supported earthretaining wall according to the preferred embodiment of the presentinvention;

FIG. 8 is a view for explaining various examples of a first pile arrayin a method for constructing a chair-type, self-supported earthretaining wall according to the preferred embodiment of the presentinvention;

FIG. 9 is a view for explaining the applicable examples of an earthanchor in a method for constructing a chair-type, self-supported earthretaining wall according to the preferred embodiment of the presentinvention;

FIG. 10 is a view for explaining an H-beam construction method in amethod for constructing an earth retaining wall according to the priorart;

FIG. 11 is a view for explaining a problem involved in the prior art;and

FIG. 12 is a view illustrating the effect of displacement caused by ahorizontal force acting on H-beams in a chair-type, self-supported earthretaining wall.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, preferred embodiments of the present invention will be describedhereinafter in detail with reference to FIGS. 1 to 9.

In the meantime, the illustration and detailed description of theconstitution, operation, and effects that can be easily understood froma general earth retaining construction technique and a related techniqueapplied to the present invention in the drawings will be omitted or onlyportions related with the present invention will be shown and described.

FIG. 1 is a schematic top plan view illustrating an earth retaining wallconstructed by a method for constructing a chair-type, self-supportedearth retaining wall according to the present invention, FIG. 2 is aview for explaining a method for constructing a chair-type,self-supported earth retaining wall according to a preferred embodimentof the present invention, FIG. 3 is a perspective view illustrating aconstitution of an earth retaining wall constructed by the method forconstructing the chair-type, self-supported earth retaining wall shownin FIG. 2, FIG. 4 is a view for explaining a method for constructing achair-type, self-supported earth retaining wall according to anotherpreferred embodiment of the present invention, FIG. 5 is a perspectiveview illustrating a constitution of an earth retaining wall constructedby the method for constructing the chair-type, self-supported earthretaining wall shown in FIG. 4, and FIG. 6 is a view for explaining asecond pile array construction method in a method for constructing achair-type, self-supported earth retaining wall according to thepreferred embodiment of the present invention.

As shown in FIG. 1, the method for constructing a chair-type,self-supported earth retaining wall according to the present inventionis provided to construct an open cut surface or an earth retaining wallfor preventing a landslide generated during the underground excavationconstruction in road construction, subway construction, new buildingconstruction, and the like. Such a method for constructing a chair-type,self-supported earth retaining wall according to the present inventionenables construction of an earth retaining wall 10 including a firstpile array 20, a second pile array 30, and a connection member 60.

In this case, a first pile array 20 of the earth retaining wall 10constructed by the method for constructing a chair-type, self-supportedearth retaining wall according to the present invention is formed byarranging a plurality of piles 22 along a circumference of theto-be-excavated region. In the present invention, the first pile array20 may be formed by applying a method of forming the second pile array30 and various construction techniques that have been previously knownin this field as in the embodiment, which will be described later. Inthis case, a plurality of piles 22 of the first pile array 20 is formedalong a circumference of the to-be-excavated region by consecutivelydrilling a plurality of boreholes 21 at predetermined intervals alongthe circumference of the to-be-excavated region, inserting H-beams 22into the respective boreholes 21, filling left and right spaces of websof the H-beams 22 with soil, and filling the outer spaces of flanges ofthe H-beams 22 with a flowable hardening material in the same manner asthe second pile array 30, which will be described later, as shown inFIGS. 2 and 4. In addition, the various construction techniques can usean H-beam and soil retaining plate, a cast-in-place pile (CIP), a PHCpile, a soil cement wall (SCW), a sheet pile, and the like.

As shown in FIGS. 2, 6 and 6, the second pile array 30 is formed byconsecutively drilling a plurality of boreholes 31 at predeterminedintervals at predetermined positions outwardly spaced apart from thefirst pile array 20 along a circumference of the to-be-excavated region,inserting H-beams 32 as a plurality of piles into the respectiveboreholes, filling left and right spaces of webs 34 of the H-beams 32with soil 40, and filling the outer spaces of flanges 36 of the H-beamswith a flowable hardening material 50. At this time, in the fillingstep, the soil 40 filled up in the left and right spaces of the webs 34includes various kinds of aggregate materials such as on-site soil, sandand fine aggregate supplied at the construction field. In addition, thesoil 40 does not need a dense filling work or a consolidation work. Likethis, the soil 40 in a loosened state provides an effect of reducing apull-out force imposed on a mechanical apparatus when pulling out theH-beam 32 to collect the H-beam 32 later, and thus the pullout isfurther facilitated. Moreover, the flowable hardening material 50 as thefilling material filled in the outer spaces of the flanges 36 of theH-beam 32 is a material that has both flowability and hardenabilitycharacteristics. This flowable hardening material 50 is excellent inflowability, and thus is well filled such that an empty space is notdefined even in a tiny space, which is difficult to fill up. Inparticular, as shown in FIG. 6, in the case where the flowable hardeningmaterial 50 is injected into the borehole 31 by pressurization, it isalso filled into a gap around the borehole 31 as shown at the rightupper side of FIG. 6, thereby achieving an effect of ameliorating theground around the borehole 31 in its entirety. Thus, it is possible toapply construction method of the present invention even in the casewhere the earth condition of the ground is poor. Since the flowablehardening material 50 has hardenability, it is well filled into theborehole 31 without forming any empty space and then becomes hardthrough a hardening reaction over time. This phenomenon exhibits asuperior effect to the performance of soil subjected to sufficientconsolidation. Therefore, the construction labor necessary for the soilconsolidation is not needed and the construction period and cost arereduced. In addition, the compression performance of a constructedportion is excellent, and thus a possibility of occurrence ofdisplacement of the self-supported earth retaining wall is furtherreduced.

Like this, after the construction of the first pile array 20 and thesecond pile array 30, the first pile array 20 and the second pile array30 are fixedly connected with each other by means of the connectionmember 60 to form a chair-type, self-supported earth retaining wall asshown in FIG. 3 or 5. In this case, the connection member 60 includes afirst girth 62 joined to the plurality of piles 22 (applying H-beams inFIGS. 1 to 5) constituting the first pile array 20 such that the piles22 are arranged in parallel with each other, a second girth 64 joined tothe plurality of H-beams 32 constituting the second pile array 30 suchthat the H-beams 32 are arranged in parallel with each other, and fixingbars 66 joined at both ends thereof to the first girth 62 and the secondgirth 64.

The earth retaining wall 10 having the above structure is formed by thefollowing method for constructing a chair-type, self-supported earthretaining wall according to the present invention. That is, as shownFIGS. 1 and 2, according to a chair-type, self-supported earth retainingwall construction method for constructing an earth retaining wall usedfor supporting an external force such as earth pressure or the like,first, a plurality of boreholes 21 is consecutively drilled atpredetermined intervals along the circumference of the to-be-excavatedregion (S200), and piles 22 are insertedly installed into the respectiveboreholes 21 (S210) to form the first pile array 20. In addition, aplurality of boreholes 31 is consecutively drilled at predeterminedintervals at predetermined positions outwardly spaced apart from thefirst pile array 20 along the circumference of the to-be-excavatedregion (S210), and H-beams 32 are insertedly installed into therespective boreholes (S220).

In this case, a borehole drilling and pile inserting apparatus 100typically used in this field is employed in the construction of theboreholes and the H-beams 22 and 32. In addition, the borehole drillingand H-beam inserting work for forming the first pile array 20 and thesecond pile array 30 will set the order and method of other work inconsideration of convenience of the work. For example, the first pilearray may be formed by a pile driving technique and other conventionalmethods. Also, in the present invention, the second pile array 30 isprovided only in the form of a single row that can be typically applied,but may be configured in the form of plural rows depending on the need,which falls within the technical spirit of the present invention.

In the meantime, as shown in FIGS. 2 and 6, in the method forconstructing a chair-type, self-supported earth retaining wall accordingto the present invention, the boreholes 31 for the second pile array 30are drilled at predetermined positions outwardly spaced apart from thefirst pile array 20 along the circumference of the to-be-excavatedregion (S210), the H-beams 32 are inserted into the boreholes such thatboth flanges 36 of the H-beams are arranged horizontally relative to theto-be-excavated region to form a second pile array 30 (S220), and soil40 is poured into a section “a” between the both flanges 36 of eachH-beam 32, i.e., spaces at both sides of the web 34 of each H-beam 32 tofill soil 40 in the section “a” between the both flanges 36 of eachH-beam 32 (S230). Thereafter, a flowable hardening material 50 issupplied to the outer spaces (i.e., sections “b”) of both flanges 36 ofeach H-beam of the second pile array 30 to fill up the outer spaces ofthe both flanges with the flowable hardening material 50 (S240).

After a predetermined time period has elapsed by the above constructionmethod, the H-beam 32 of the second pile array 30 is stably supportedwithin the borehole 31 by means of the soil 40 filled in the section “a”and the flowable hardening material 50 filled in the section “b”, sothat displacement of the H-beam 32 can be effectively prevented and theflowable hardening material 50 filled in the section “b” can be easilyseparated from the H-beam 32 when the H-beam 32 is pulled out to becollected, thereby making the-use of the H-beam 32 convenient.

More specifically, referring to FIG. 6, in the preferred embodiment ofthe present invention, the H-beam 32 used in the second pile array 30 isH-300×300×10×15 in size, and the borehole 31 is 450 mm in diameter. Inthis case, a clearance distance ranging from about 1 cm to 8 cm issecured in the borehole 31 for insertion of the H-beam 32. In a statewhere the H-beam 32 is inserted into the borehole 31, a process offilling up the borehole 31 consists of two steps. A first step is one inwhich soil 40 consisting of on-site soil, sand or other fillingaggregate is supplied to the section “a” between the both flanges 36 ofeach H-beam 32 of the second pile array 30 to fill up the soil 40 in thesection “a” (S230). Also, a second step is one in which the flowablehardening material 50 is supplied to the outer spaces (i.e., sections“b”) of both flanges 36 of each H-beam 32 of the second pile array 30 tofill up the outer spaces of the both flanges with the flowable hardeningmaterial 50 such as cement paste, soil cement, or the like (S240). Ofcourse, the first step (S230) and the second step (S240) may be changedin the construction order or may be performed simultaneously.

In the filled H-beam 32 of the second pile array 30, the flowablehardening material 50 is filled up in the sections “b” of both flangesof each H-beam 32 in a state where the flowable hardening material 50flows. When the flowable hardening material 50 is hardened over time, itbecomes a filling material having a deformation resistance capabilityhigher than that of consolidated soil. In addition, the soil 40 filledup in the section “a” between the both flanges 36 of each H-beam 32 isnot subjected to an additional consolidation process and is maintainedin a relaxed and loosened state, but is positioned at both sides of theweb 34 (see FIG. 6) of the H-beam 32. Thus, the filled soil 40 isirrelevant to occurrence of displacement of the H-beam 32 toward theearth retaining wall. Owing to the loosened soil 40 positioned at theboth sides of the web 34, the H-beam 32 is readily pulled out to becollected. In addition, since a lump of the flowable hardening material50 is prevented from adhering to the web 34 thanks to the filled soil, acollection work for reuse of the H-beam 32 is much facilitated.

Therefore, according to the method for constructing a chair-type,self-supported earth retaining wall of the present invention, thedisplacement occurrence in a double-row pile construction technique isgreatly restricted, the pullout work of the H-beam 32 is facilitated forthe reuse of the H-beam 32 as a temporary facility constructing steelsheet, and the necessity of cleaning and washing the H-beam iseliminated, thereby improving the construction capacity and economicefficiency of the construction method and removing a displacementinducing factor that is, inter alia, important, which results inachievement of an effect to significantly improve the performance of theconstruction method.

In this case, in the present invention, the H-beams (e.g., H-piles) thatare particularly used in the second pile array 30 are referred to a beamhaving an H-shaped transverse cross-section. However, the shape of thetransverse cross-section is not limited thereto, and the H-beams may bereferred to as I-section steels, asymmetrical H-beams and various shapesof piles, which are proposed pursuant to provisions of each country inconnection with the present invention.

In addition, for the order in which the soil 40 and the flowablehardening material 50 are supplied, preferably, the soil 40 is firstsupplied, but is not limited thereto. Also, in consideration ofcontinuity of the use of a construction equipment, all the H-beams 32 ofthe second pile array 30 are inserted into the boreholes 31, and thenthe soil 40 and the flowable hardening material 50 are preferablysupplied sequentially, but is also not limited thereto. Each step of theprocess can be processed in various forms in consideration of the worksituation of the construction site in conformity with the technicalspirit of the present invention. Besides, in the present invention, thesoil 40 is preferably supplied by applying on-site soil, but may beselected from the group consisting of on-site soil, sand, otheraggregate, and the like. In the present invention, the flowablehardening material 50 may be preferably cement paste, soil cement or thelike.

In this manner, after the first pile array 20 and the second pile array30 are formed, the first pile array 20 and the second pile array 30 areallowed to be fixedly connected with each other by means of theconnection member 60 in consideration of two steps (S250 and, S250′).That is, as shown in FIGS. 2 and 3, in one step (S250), the connectionmember 60 is installed in such a fashion that the first girth 62 isjoined to the plurality of piles 22 constituting the first pile array 20such that the piles 22 are arranged in parallel with each other on theground before excavating the ground of the to-be-excavated region, thesecond girth 64 is joined to the plurality of piles 32 constituting thesecond pile array 30 such that the piles 32 are arranged in parallelwith each other, and fixing bars 66 are mounted on the first girth 62and the second girth 64 in such a fashion as to be joined at both endsthereof to the first girth 62 and the second girth 64. In this case, inFIGS. 2 and 3, there is shown an example in which the H-beams 22 and theloggings 70 are applied to the first pile array 20. In the case wherethe first pile array 20 is formed by various construction techniques asshown in FIG. 8, the piles 22 of the first pile array 20 referred to inthe present invention correspond to H-beams 22, 22 c and 22 d and asheet 22 b functioning as the piles in each construction technique.

In another step (S250′), as shown in FIGS. 4 and 5, the connectionmember 60 is installed in the above-mentioned form on the ground of thesub-excavation region in such a fashion that a sub-region to beexcavated (also, called a “sub-excavation region”) communicatingextending from the second pile array 30 on the ground to theto-be-excavated region is formed during excavation of theto-be-excavated region, and a logging 80 is joined to the second pilearray 30 while forming the sub-excavation region along the second pilearray 30. In this case, the sub-excavation region is referred to as aspace of a stepped shape defined between the first pile array 20 and thesecond pile array 30 as shown in FIGS. 4 and 5. This step has an effectof capable of reducing an influence of earth pressure on the lowerportion of the to-be-excavated region.

The connection member 60 is designed to have a self-supported structureformed by fixedly interconnecting the first pile array 20 and the secondpile array 30 arranged at predetermined intervals in such a fashion asto be outwardly spaced apart from each other along the circumference ofthe to-be-excavated region. In this case, the connection member canadopt various kinds of materials including sectional steel, bar steel,deformed steel bar, and the like. The first girth 62, the second girth60 and the fixing bars 66 of the connection member 60 are joined to oneanother by means of welding, bolts, couplers, or the like, and arefixedly mounted on the respective H-beams 22 and 32 of the first andsecond pile arrays 20 and 30 by means of brackets 68 (see FIG. 3). Inaddition, although not shown, a brace may be constructed together withthe fixing bars 66 to reinforce a restraint force of the fixing bars 66.A method of joining the first girth 62, the second girth 60 and thefixing bar 66 mainly employs a bolt engagement manner for the sake ofthe convenience of the construction and the dismantling of the temporaryfacility structures. But other joining methods including welding andcouplers can be selected to conform to the conditions of theconstruction site depending on the need.

Then, like a typical earth retaining wall, loggings 70 are mounted onthe inner side of the to-be-excavated region along with excavation ofthe to-be-excavated region (S260).

FIG. 7 is a view for explaining the applicable examples of a connectionmember in a method for constructing a chair-type, self-supported earthretaining wall according to the preferred embodiment of the presentinvention, FIG. 8 is a view for explaining various examples of a firstpile array in a method for constructing a chair-type, self-supportedearth retaining wall according to the preferred embodiment of thepresent invention, and FIG. 9 is a view for explaining the applicableexamples of an earth anchor used along with a conventional constructiontechnique in a method for constructing a chair-type, self-supportedearth retaining wall according to the preferred embodiment of thepresent invention.

Referring to FIG. 7, the connection member 60 applied to the method forconstructing a chair-type, self-supported earth retaining wall accordingto the preferred embodiment of the present invention may be disposed onthe ground of the sub-excavation region defined by excavating to apredetermined depth between the piles 22 of the first pile array and thepiles 32 of the second pile array (see FIG. 7( a)), or may be disposedon the ground before excavating the ground of the to-be-excavated regionas described above. In addition, as shown in FIGS. 7( c) and 7(d), themethod for constructing a chair-type, self-supported earth retainingwall according to the present invention may adopt an auxiliaryconnection member 60′ by employing various methods used for the purposeof reinforcement in this field.

Referring to FIG. 8, as described above, the method for constructing achair-type, self-supported earth retaining wall according to thepreferred embodiment of the present invention may adopt a method ofapplying the first pile array (see FIG. 2) to the second pile array 20(see FIG. 2) of the present invention, or various construction methodsthat are well known in this field. In other words, in FIG. 8( a), thereis shown an applicable form of a construction technique of loggings andair piles formed by driving the H-beams 22 into the ground along thecircumference of the to-be-excavated region or inserting the H-beams 22into previously bored boreholes, and then fitting loggings 70 betweenthe adjacent H-beams 22. In addition, in FIG. 8( b), there is shown anapplicable form of the sheet pile construction technique ofconsecutively forming a number of sheet piles 22 b along thecircumference of the to-be-excavated region in such a fashion that thejoints of the sheet piles 22 b are engaged with each other, and thendriving the sheet piles 22 b in the underground using a drivingapparatus to thereby form the earth retaining wall. Moreover, in FIG. 8(c), there is shown an applicable form of the cast-in-place pileconstruction technique of consecutively forming a number of boreholes atgiven intervals along the circumference of the to-be-excavated region,filling up prefabricated bar mats 22 c′ and coarse aggregate in theboreholes, and injecting mortar or pouring concrete into the boreholes.Further, in FIG. 8( d), there is shown an applicable form of the soilcement wall construction technique of disposing a cutter at a front endof a pipe stirring shaft of a boring equipment and excavating the groundwhile mixing a hardening material and soil, erupting cement milk at afront end of the excavation device, and pulling out the pipe whilemixing soil and mortar to thereby form a continuous pile wall. Likewise,the method for constructing a chair-type, self-supported earth retainingwall according to the preferred embodiment of the present invention hasan advantage in that since the first pile array 20 can be constructed byapplying various construction techniques, the construction range of thepresent invention can be easily extended. Of course, the work of thegirths and the fixing bars for installation of the connection member isalso applied. In this embodiment, H-piles and soil retaining plates,sheet piles, cast-in-place piles, soil cement walls, and the like forformation of the plurality of piles 22 of the first pile array 20 areconstruction techniques that are widely known in the art. Suchconstruction techniques including a chemical grouting method such asLabiles Wasserglass (LW) grouting can be selected and combined dependingon the need of a client or a person of ordinary skill in the art, andthus their detailed description will be omitted to avoid redundancy.

Referring to FIG. 9, the method for constructing a chair-type,self-supported earth retaining wall according to the preferredembodiment of the present invention has an advantage of effectivelyincreasing the excavation depth of the to-be-excavated region byadopting a soil nailing technique that is typically applied to increasethe bearing capacity of the earth retaining wall 10 in the art. That is,conventionally, the earth anchor 100 has been also applied in theconstruction of the earth retaining wall, but the method forconstructing a chair-type, self-supported earth retaining wall accordingto the present invention has an advantage in that it enables moreeffective deep excavation while reducing the number of the earth anchors100. In this case, the construction and operation of the earth anchor100 is previously widely known in the art, and thus its detaileddescription will be omitted for brevity.

While the method for constructing a chair-type, self-supported earthretaining wall according to the preferred embodiments of the presentinvention has been described and illustrated in connection with specificexemplary embodiments with reference to the accompanying drawings, itwill be readily appreciated by those skilled in the art that it ismerely illustrative of the preferred embodiments of the presentinvention and various modifications and changes can be made theretowithin the technical spirit and scope of the present invention.

BEST MODE

As shown in FIG. 1, the method for constructing a chair-type,self-supported earth retaining wall according to the present inventionis provided to construct an open cut surface or an earth retaining wallfor preventing a landslide generated during the underground excavationconstruction in road construction, subway construction, new buildingconstruction, and the like. Such a method for constructing a chair-type,self-supported earth retaining wall according to the present inventionenables construction of an earth retaining wall 10 including a firstpile array 20, a second pile array 30 and a connection member 60.

In this case, a first pile array 20 of the earth retaining wall 10constructed by the method for constructing a chair-type, self-supportedearth retaining wall according to the present invention is formed byarranging a plurality of piles 22 along a circumference of theto-be-excavated region. In the present invention, the first pile array20 may be formed by applying a method of forming the second pile array30 and various construction techniques that have been previously knownin this field as in the embodiment, which will be described later. Inthis case, a plurality of piles 22 of the first pile array 20 is formedalong a circumference of the to-be-excavated region by consecutivelydrilling a plurality of boreholes 21 at predetermined intervals alongthe circumference of the to-be-excavated region, inserting H-beams 22into the respective boreholes 21, filling left and right spaces of websof the H-beams 22 with soil, and filling the outer spaces of flanges ofthe H-beams 22 with a flowable hardening material in the same manner asthe second pile array 30, which will be described later, as shown inFIGS. 2 and 4. In addition, the various construction techniques can usean H-beam and soil retaining plate, a cast-in-place pile (CIP), a PHCpile, a soil cement wall (SCW), a sheet pile, and the like

As shown in FIGS. 2, 6 and 6, the second pile array 30 is formed byconsecutively drilling a plurality of boreholes 31 at predeterminedintervals at predetermined positions outwardly spaced apart from thefirst pile array 20 along a circumference of the to-be-excavated region,inserting H-beams 32 as a plurality of piles into the respectiveboreholes, filling left and right spaces of webs 34 of the H-beams 32with soil 40, and filling the outer spaces of flanges 36 of the H-beamswith a flowable hardening material 50. At this time, in the fillingstep, the soil 40 filled up in the left and right spaces of the webs 34includes various kinds of aggregate materials such as on-site soil, sandand fine aggregate supplied at the construction field. In addition, thesoil 40 does not need a dense filling work or a consolidation work. Likethis, the soil 40 in a loosened state provides an effect of reducing apull-out force imposed on a mechanical apparatus when pulling out theH-beam 32 to collect the H-beam 32 later, and thus the pullout isfurther facilitated. Moreover, the flowable hardening material 50 as thefilling material filled in the outer spaces of the flanges 36 of theH-beam 32 is a material that has both flowability and hardenabilitycharacteristics. This flowable hardening material 50 is excellent inflowability, and thus is well filled such that an empty space is notdefined even in a tiny space which is difficult to fill up. Inparticular, as shown in FIG. 6, in the case where the flowable hardeningmaterial 50 is injected into the borehole 31 by pressurization, it isalso filled into a gap around the borehole 31 as shown at the rightupper side of FIG. 6, thereby achieving an effect of ameliorating theground around the borehole 31 in its entirety. Thus, it is possible toapply construction method of the present invention even in the casewhere the earth condition of the ground is poor. Since the flowablehardening material 50 has hardenability, it is well filled into theborehole 31 without forming any empty space and then becomes hardthrough a hardening reaction over time. This phenomenon exhibits asuperior effect to the performance of soil subjected to sufficientconsolidation. Therefore, the construction labor necessary for the soilconsolidation is not needed and the construction period and cost arereduced. In addition, the compression performance of a constructedportion is excellent, and thus a possibility of occurrence ofdisplacement of the self-supported earth retaining wall is furtherreduced.

Like this, after the construction of the first pile array 20 and thesecond pile array 30, the first pile array 20 and the second pile array30 are fixedly connected with each other by means of the connectionmember 60 to form a chair-type, self-supported earth retaining wall asshown in FIG. 3 or 5. In this case, the connection member 60 includes afirst girth 62 joined to the plurality of piles 22 (applying H-beams inFIGS. 1 to 5) constituting the first pile array 20 such that the piles22 are arranged in parallel with each other, a second girth 64 joined tothe plurality of H-beams 32 constituting the second pile array 30 suchthat the H-beams 32 are arranged in parallel with each other, and fixingbars 66 joined at both ends thereof to the first girth 62 and the secondgirth 64.

The earth retaining wall 10 having the above structure is formed by thefollowing method for constructing a chair-type, self-supported earthretaining wall according to the present invention. That is, as shownFIGS. 1 and 2, according to a chair-type, self-supported earth retainingwall construction method for constructing an earth retaining wall usedfor supporting an external force such as earth pressure or the like,first, a plurality of boreholes 21 is consecutively drilled atpredetermined intervals along the circumference of the to-be-excavatedregion (S200), and piles 22 are insertedly installed into the respectiveboreholes 21 (S210) to form the first pile array 20. In addition, aplurality of boreholes 31 is consecutively drilled at predeterminedintervals at predetermined positions outwardly spaced apart from thefirst pile array 20 along the circumference of the to-be-excavatedregion (S210), and H-beams 32 are insertedly installed into therespective boreholes (S220).

In this case, a borehole drilling and pile inserting apparatus 100typically used in this field is employed in the construction of theboreholes and the H-beams 22 and 32. In addition, the borehole drillingand H-beam inserting work for forming the first pile array 20 and thesecond pile array 30 will set the order and method of other work inconsideration of convenience of the work. For example, the first pilearray may be formed by a pile driving technique and other conventionalmethods. Also, in the present invention, the second pile array 30 isprovided only in the form of a single row that can be typically applied,but may be configured in the form of plural rows depending on the need,which falls within the technical spirit of the present invention.

In the meantime, as shown in FIGS. 2 and 6, in the method forconstructing a chair-type, self-supported earth retaining wall accordingto the present invention, the boreholes 31 for the second pile array 30are drilled at predetermined positions outwardly spaced apart from thefirst pile array 20 along the circumference of the to-be-excavatedregion (S210), the H-beams 32 are inserted into the boreholes 31 suchthat both flanges 36 of the H-beams are arranged horizontally relativeto the to-be-excavated region to form a second pile array 30 (S220), andsoil 40 is poured into a section “a” between the both flanges 36 of eachH-beam 32, i.e., spaces at both sides of the web 34 of each H-beam 32 tofill soil 40 in the section “a” between the both flanges 36 of eachH-beam 32 (S230). Thereafter, a flowable hardening material 50 issupplied to the outer spaces (i.e., sections “b”) of both flanges 36 ofeach H-beam of the second pile array 30 to fill up the outer spaces ofthe both flanges with the flowable hardening material 50 (S240).

After a predetermined time period has elapsed by the above constructionmethod, the H-beam 32 of the second pile array 30 is stably supportedwithin the borehole 31 by means of the soil 40 filled in the section “a”and the flowable hardening material 50 filled in the section “b”, sothat displacement of the H-beam 32 can be effectively prevented and theflowable hardening material 50 filled in the section “b” can be easilyseparated from the H-beam 32 when the H-beam 32 is pulled out to becollected, thereby making the-use of the H-beam 32 convenient.

INDUSTRIAL APPLICABILITY

The method for constructing a chair-type, self-supported earth retainingwall according to the present invention is provided to construct an opencut surface or an earth retaining wall for preventing a landslidegenerated during the underground excavation construction in roadconstruction, subway construction, new building construction, and thelike.

1. A method for constructing a chair-type, self-supported earthretaining wall used for supporting external forces such as earthpressure, the method comprising the steps of: forming a first pile arrayhaving a plurality of piles arranged along a circumference of an regionto be excavated; forming a second pile array having a plurality of pilesarranged along a circumference of the to-be-excavated region byconsecutively drilling a plurality of boreholes at predeterminedintervals at predetermined positions outwardly spaced apart from thefirst pile array along the circumference of the to-be-excavated region,inserting H-beams into the respective boreholes, filling left and rightspaces of webs of the H-beams with soil, and filling the outer spaces offlanges of the H-beams with a flowable hardening material; and fixedlyinterconnecting the first pile array and the second pile array using aconnection member, whereby the first pile array and the second pilearray are formed in such a fashion as to be outwardly spaced apart fromeach other along the circumferences of the to-be-excavated region, andare connected to each other by the connection member to construct anunderground earth retaining wall.
 2. The method according to claim 1,wherein the plurality of piles of the first pile array is formed byconsecutively drilling a plurality of boreholes at predeterminedintervals along the circumference of the to-be-excavated region,inserting H-beams into the respective boreholes, filling left and rightspaces of webs of the H-beams with soil, and filling the outer spaces offlanges of the H-beams with a flowable hardening material.
 3. The methodaccording to claim 2, wherein the plurality of piles of the first pilearray is formed of any one selected from the group consisting of H-pilesand soil retaining plates, sheet piles, cast-in-place piles, and soilcement walls.
 4. The method according to any one of claims 1 to 3,wherein the step of fixedly interconnecting the first pile array and thesecond pile array using a connection member comprises the followingsteps of: joining a first girth to the plurality of piles constitutingthe first pile array such that the piles are arranged in parallel witheach other on the ground before excavating the ground of theto-be-excavated region; joining a second girth to the plurality of pilesconstituting the second pile array such that the piles are arranged inparallel with each other; and mounting fixing bars on the first girthand the second girth in such a fashion as to be joined at both endsthereof to the first girth and the second girth.
 5. The method accordingto any one of claims 1 to 3, wherein the step of fixedly interconnectingthe first pile array and the second pile array using a connection membercomprises the following steps of: forming a sub-excavation regioncommunicating extending from the second pile array on the ground to theto-be-excavated region during excavation of the to-be-excavated region;joining loggings to the second pile array while forming thesub-excavation region along the second pile array; joining a first girthto the plurality of piles constituting the first pile array such thatthe piles are arranged in parallel with each other on the ground of thesub-excavation region; joining a second girth to the plurality of pilesconstituting the second pile array such that the piles are arranged inparallel with each other; mounting fixing bars on the first girth andthe second girth in such a fashion as to be joined at both ends thereofto the first girth and the second girth; and joining loggings to thefirst pile array while forming the to-be-excavated region along thefirst pile array.